Process for making tetramethyl lead



United States Patent Ofifice 3,281,442 Patented Oct. 25, 1966 PROCESS FOR MAKING TETRAMETHY L LEAD Rudolph L. Pedrotti, Newark, and Charles A. Sandy, Wilmington, DeL, assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware N Drawing. Filed July 5, 1963, Ser. No. 293,138

11 Claims. (Cl. 260-437) This invention relates to the manufacture of tetramethyl lead, more particularly to its manufacture by the reaction of methyl chloride with monosod-ium lead alloy in the presence of a novel catalyst system which is highly effective under mild conditions of temperature and pressure.

Recent trends in the formulation of motor gasoline have created a significant demand for tetramethy-l lead as an antiknock agent. However, as disclosed in the recent ar-t, for example by Jarv-ie et al. in U.S. Patent 3,048,610, Tullio in US. Patents 3,072,694 and 3,072,695, and Cook et al. .in US. Patent 3,049,558 the manufacture of tetramethyl lead by the reaction of methyl chloride with sodium lead alloy presents considerable difficulties. In direct contrast to the well-known ethyl chloride-sodium lead alloy system, which does not require catalysis below 100 C. but can be accelerated by ketones, alcohols, esters and other substances known to the art as ethylation accelerators, the methyl chloride-sodium lead alloy system responds not at all to conditions normally conducive to the formation of tetraethy-l lead. In fact, from the disclosures of the recent practitioners of the art, it appears that methylation of sodium lead alloy is unique in that only certain catalysts of the aluminum type have been found to be eifective. Such high degree of catalyst specificity appears characteristic also of the mixed methylation-ethylat-ion of sodium lead alloys as disclosed by Calingaert et al. in US. Patent 2,270,109.

In general then, it appears from the art that a catalyst effective for ethylation is not necessarily effective for methylation. It is also apparent from the above patents, which are directed particularly and solely to the manufacture of tetramethyl lead, that the aluminum-type catalysts represent the best heretofore known means for effecting reaction of methyl chloride with sodium lead aly. Such substances are now used in commercial processes for the manufacture of tetramethyl lead. However, they have major drawbacks. The require elevated temperatures at long reaction times, norm-ally temperatures on the order of 100 C. for several hours. Such conditions, in view of the high vapor pressure of methyl chloride, necessitate the use of expensive pressure systems for practical and safe operation. Also, they add to the hazards already inherent in the handling of tetramethyl lead in that they form in the reaction system alkyl aluminum derivatives which are extremely sensitive to air and moisture and tend to ignite spontaneously on exposure to the atmosphere.

It should be noted that the processes of Jarvie et al. and Tullio, though providing for relatively smooth and safe initiation of the aluminum-catalyzed system whereby sorne of the hazards are alleviated, are not entirely satisfactory in that they still require elevated temperatures for completion of the methylation reaction and do not completely avoid the hazards inherent in handling alkyl aluminum systems.

Thus, the large scale manufacture of tetramethyl lead has continued to present extremely sensitive and serious problems.

It is an object of this invention to provide a new and improved process for the manufacture of tetramethyl lead. Another object is to provide such a process which is particularly adapted for the large scale manufacture of pure tetramethyl lead. A further object is to effect the reaction of methyl chloride with monosodium lead alloy in an improved manner which mitigates the fire and explosion hazards inherent in the use of the prior art catalyst systems based on aluminum. A particular object is to provide a catalytic process for reacting methyl chloride with mon-osodium lead alloy wherein the reaction is initiated smoothly and safely at relatively low temperatures and proceeds rapidly and smoothly under relatively mild conditions of temperature and pressure to produce tetramethyl lead in high yields. Other objects are to advance the art. Still other objects will appear hereinafter.

The above and other objects of this invention will be accomplished by the process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) A methylating agent which consists essentially of methyl chloride in the liquid phase, employing at least about 1 mole of methyl chloride per mole of alloy,

(B) At a temperature of from about 20 C. to about 120 C.

(C) In the presence of a catalyst system which consists essentially of (a) From 0.01 to about 1.5 moles of ammonia per mole of alloy,

(b) From 0 to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride, and

(c) From 0 to 0.04 mole per mole of alloy of a monohydroxylic organic compound of the formula ROH wherein R represents a member of the group consisting of hydrocarbon and oxahydrocarbon radicals of 1-18 carbon atoms.

In preferred embodiments, the reaction is effected with about 1.3 to about 3 moles of MeCl, about 0.05 to about 0.6 mole of NH and about 0.00014 to about 0.025 mole of H 0, provided that the total amount of water does not exceed 0.3% by weight (3000 ppm.) of the methyl chloride, and/or about 0.0003 to about 0.025 mole of monohydroxylic organic compound, at temperatures of from about 25 C. to about C. and at pressures of from about to about 300 p.s.i.g. (pounds per square inch gauge). It is particularly preferred to operate at about 35 C. to about 60 C. and about 100 to about p.s.i.g. The abbreviation ppm. means parts per million by weight, i.e. the indicated number of parts per million parts of methyl chloride.

By this process, the methylation is initiated and brought to completion smoothly and rapidly under mild conditions. In general, temperatures can be lower and reaction times shorter, while the yields of tetramethyl lead are as high or higher than in the recently patented processes of Jarvie et al., Tullio and Cook et al., involving aluminum-based catalyst systems. Moreover, the catalyst systems of this invention avoid the hazards involved in handling and processing the aluminum catalysts and the reaction masses produced therefrom. Thus, the manufacture of tetramethyl lead is made significantly more safe, practical and economic.

The presence of ammonia in the catalyst system is critical. Without it, practically no tetramethyl lead is produced. Broadly, the quantity of ammonia will correspond to 0.01 to about 1.5 moles per mole of alloy, the actual amount depending on such factors as the amount of methyl chloride used, the temperature and time of reaction and the nature and proportion of the co-catalyst components. More usually, the molar ratio of ammonia to alloy ranges from about 0.05 to about 0.6. In general, the lower the ammonia to alloy ratio the higher the specificity of the reaction, that is, the

higher the ratio of the conversion of alloy to tetramethyl lead to the total conversion of alloy to all products, less alloy being consumed in side reactions to produce other products. On the other hand, sufficient ammonia is normally needed to provide reasonable rates of tetramethyl lead formation. The reaction variables are easily coordinated to produce tetramethyl lead radidly in high yields under extremely mild conditions of temperature and pressure. For example, particularly good results are obtained in the preferred embodiments with ammonia to alloy molar ratios in the range of about 0.05 to about 0.3 at temperatures of from about C. to about 85 C.

It has also been discovered that water or a monohydroxylic organic compound in controlled proportions as defined can exert a marked co-catalytic effect to increase the rate of the ammonia-catalpzed methylation reaction :and/or the specificity of that reaction. Thus, in contrast to prior practice regarding the alkylation of monosodium lead alloy, it is not critical for practical operation to exclude or limit moisture to very low levels. This has a commercially important advantage because the -methyl chloride ordinarily contains small amounts of water and it is not economically practical to provide completely anhydrous methyl chloride. Methyl chloride, containing 50 ppm. or less of water, is generally considered in this art to be substantially anhydrous. For example, in the methylation reaction involving aluminum-type catalysts,

vit is normally considered desirable to limit the water content of the methyl chloride to less than about 150 ppm. water (0.015% wt.) and in general to operate as anhydrously as possible. Substantially larger water levels may, if desired, be present in the methyl chloride according to the present invention, for example on the order of 500 to 3000 ppm, 0.05% to 0.3% by weight, provided of course the total Water introduced into the reaction mixture does not amount to more than about 0.04 mole per mole of alloy and does not exceed about 0.3% by weight of the MeCl. The presence of gross water tends to depress the yields of tetramethyl lead markedly. Preferred water to alloy ratios are in the range 000014-0025 mole. Based on MeCl, the preferred range is about 50 to about 3000 p.p.m., about 0.005% to about 0.3% by weight, particularly about 100 to about 1000 p.p.m., about 0.01% to about 0.1% by weight.

There may also be used as defined, in conjunction with said water, or alone as the sole ammonia activator, one or more monohydroxylic organic compounds composed of carbon, hydrogen and one or more oxygens, and containing up to 18 carbon atoms, and no oxygens other than ether and hydroxyl oxygens. In other words, the hydroxylic component need only contain one hydroxyl group and be otherwise essentially inert as far as the alloy is concerned, that is, contain only hydrocarbon and oxahydrocarbon radicals. Also, the monohydroxylic organic compound can be defined as a compound of the formula ROH wherein R is a hydrocarbon or an oxahydrocarbon radical of 1-18 carbon atoms, said oxa designation standing for ether oxygen. Thus, there may be used a variety of aliphatic and cycloaliphatic alcohols consisting of, in addition to said OH group, hydrocarbon or etherhydrocarbon radicals. Similarly, there may be used phenol and phenols containing hydrocarbon and etherhydrocarbon substituents. The activating effect appears to be specific to the monohydroxylic compounds, corresponding polyhydroxylic compounds appearing to have little or no activating or promoting effect.

Representative monohydroxylic organic compounds are the simple alkanols and cycloalkanols such as methanol, ethanol, 1- and 2-propanol, l-butanol, 2-methyl-2-propanol, pentanol, hexanol, 3,5,5-trimethylhexanol, cyclopentanol and cyclohexanol; naturally-occurring fatty alco hols such as the mixtures derived from coconut oil for example and including decanol, dodecanol (lauryl alcohol), tetradecanol (myristyl alcohol), hexadecanol (cetyl alcohol and octadecanol (stearyl alcohol); alcohols made by the 0x0 process such as oxo-octyl alcohol and 0x0- tridecanol; unsaturated alcohols such as allyl alcohol, oleyl alcohol and propargyl alcohol; ether alcohols such as ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and diethylene glycol monomethyl ether; phenolics such as phenol, o-, mand p-cresol, the xy-lenols, p-nonyl phenol, and resorcinol monomethyl ether. Mixtures of any two or more of the monohydroxylic organic compounds may be used.

Methanol or other lower alkanol (of 1-4 carbon atoms) is highly preferred for it is particularly effective as an activator for the ammonia component both to accelerate the methylation reaction and to favor the formation of tetramethyl lead at the expense of side reaction such as those leading to volatile hydrocarbons.

Such monohydroxylic component may be present in molar proportions as high as about 0.04 mole per mole of alloy, preferably from about 0.0003 to about 0.025 mole per mole of alloy. Also preferably and more usu ally, the combined (total) amount of water and monohydroxylic organic compound will not exceed about 0.04 mole per mole of alloy.

The term methyl halide methylating agent consisting essentially of methyl chloride includes methyl chloride as the essential source of methyl groups and mixtures thereof with up to about 5 mole percent of methyl iodide based on the methyl chloride, more usually less than about 1 mole percent of said methyl iodide. Such small proportions of such methyl iodide, e.g. 0.1-1 mole percent may have beneficial effects. For example, methyl iodide appears effective at low temperatures in conjunction with said ammonia catalyst to accelerate the methylation reaction and thereby increase the rate of production of tetramethyl lead. While the iodide may be present in small proportions as above, the ammonia catalyzed process appears unique for methyl chloride as the essential methylating agent.

The methylating agent is normally employed in amounts of at least about one mole and usually not more than about 5 moles per mole of alloy. Larger quantities, up to 20 moles, may be used but are not necessary. Preferred ratios are in the range of about 1.3 to about 3 moles of methyl chloride per mole of alloy.

The monosodium lead alloy (NaPb) to be used in this process, i.e. containing 50 mole percent Na and 50 mole percent Pb, or on a weight basis 10% wt. Na and wt. Pb, has been amply described in the art. It may be used in various forms, usually comminuted, including ground as disclosed by Stecher in U.S. Patent 2,134,091, flaked as disclosed by Pyk in U.S. Patent 2,561,636 or by Tanner in U.S. Patent 2,635,107, and quenched (in MeCl) as described by Mattison in U.S. Patent 2,744,126.

Broadly, the overall process comprises (1) mixing the alloy, methyl halide, ammonia and, when desired, water or other monohydroxylic co-catalyst component, (2) holding such mixture at a temperature in the range of 20 C. to about C. at which the reaction is initiated and proceeds at a reasonable rate, and (3) recovering the tetramethyl lead from the reaction mass. Normally, the reaction is effected under agitation and it is usually desirable toeffect the reaction in the presence of an inert solid, such as graphite, as an internal lubricant. From about 1% to about 5% by weight of graphite based on the alloy may be used, depending on the dimensions of the reactor, the effectiveness of the agitation means, and the proportions of the reactants. There may also be present, a thermal stabilizer for tetramethyl lead, as described in the art by Jarvie et al. in U.S. Patent 3,048,- 610 and Cook et al. in U.S. Patent 3,049,558, for example a volatile hydrocarbon such as toluene or isooctane having boiling characteristics comparable to those of tetramethyl lead.

The reactants, catalyst components and other agents (as described above) may be introduced separately or together, all at once or gradually during the course of the reaction. The ammonia and the co-catalyst components may be added as such or in a carrier which conveniently may be the methylating agent or an inert solvent including the thermal stabilizers toluene and isooctane. Ammonia, normally gaseous like methyl chloride, may be charged to the react-or as condensed liquid or as pressurized vapor.

The reaction mass components may be mixed at low temperatures at which the reaction does not proceed at a substantial rate, e.g. at 70 C. or below, and the mixture then brought to operating temperatures. Or the reactants and other essential components may be brought into contact at temperatures within the operating range, preferably in the preferred 25 C. to -85 C. range. The reaction may be conducted b-atchwise or continuously.

I An important feature of this invention is that the ammonia-catalyst system effects the methylation reaction at low temperatures and low pressures. Reaction mass temperatures are readily controlled by controlling the amount and schedule of catalyst and methyl chloride addition, by cooling where necessary and by refluxing methyl chloride, to keep the internal pressure at desired levels, suffi cient to maintain the methyl chloride in liquid phase or under reflux pressure, for example below 300 p.s.i.g. Indeed, attemperatures of from 25 C. to 85 C., pressures are easily maintained in the 100-300 p.s.i.g. region. Of

values of Y/ C, times 100, being the percent alloy consumed in side reactions.

The following examples are given to more fully illustrate the invention, preferred modes of operation, and the advantageous results to be obtained thereby. The quantities are in parts by weight unless otherwise noted.

Example 1 The data, shown in Table 1 below, were obtained according to the following procedure, involving a stainless steel pressure reactor equipped with outer electrical heating means and inner thermocouples for measuring temperature, and adapted for agitation by shaking. The reactor volume is such that 100 parts MeCl corresponds to a loading density of 0.25 gr./ cc.

One hundred parts crushed NaPb and 4.3 parts toluene were added to the reactor under nitrogen. The reactor was then closed, cooled to 70 C. and evacuated. Then, in turn, ammonia, to provide concentrations as tabulated below, and 69 parts of methyl chloride, containing 60 p.-p.-m. H O, were weighed in from pressurized supplies. Agitation was started and the reaction mixture brought to reaction temperature in 5 to 10 minutes and held there for the time periods indicated below. Reaction was terminated by cooling to -70 C. Tetramethyl lead was recovered by extracting the reaction product with toluene.

Typical results, obtained under various conditions of temperature, ammonia concentration, and reaction time are shown in Table I.

TABLE I.-AMMONIA CATALYZED MeCl-NaPb REACTION [Molar MeCl/NaPb =31; molar H 0/NaPb =0.0005] N11 Concentration Time, Run Temp., 0. Hours Y, Percent C, Percent Y/C Percent Wt. Mole/Mole Alloy NaPb *The temperature was raised from 70 C. to -20 C. during minutes from the time the methyl chloride was introduced; and the reaction mixture was agitated only for the middle third of the 45 minutes period.

involved in having a relatively unstable product, suchas tetramethyl lead, confined at elevated temperatures.

The resulting reaction mass may be worked up in the usual ways described in the art. Normally, the residual methyl chloride is vented from the charge at a temperature in the range of about 25 C. to about C., and passed to a recovery system as in tetraethyl lead technology. For this purpose, the temperature of the reac tion mixture is adjusted accordingly, if necessary. The tetramethyl lead product is then recovered by solvent extraction, e.g. with toluene, or by steam distillation according to the well-known techniques.

In the examples, Y, percent is the percent of the theoretical yield of tetramethyl lead based on the quantity of alloy employed; C, percent is the total percent of the alloy consumed by reaction to produce tetramethyl lead and other products, and Y/ C is the ratio of the percent yield of tetramethyl lead (and of the percent of the alloy that is consumed in producing tetramethyl lead) to the total percent alloy consumed in all reactions. Thus, Y/ C is a measure of the reaction specificity to produce tetramethyl lead, the difierence between 1.00 and the given The data show that, while the process is broadly operable over a wide range of conditions, the use of relatively low NH concentrations and moderate temperatures provides better overall results in terms yield (Y) and efiiciency (Y/ C).

Example 2 The following test procedure was employed to further illustrate the method of the invention and the advantageous results to be obtained thereby under mild con ditions.

A steel bomb was charged with parts of crushed monosodium lead alloy enclosed in a glass ampoule. Then with the bomb cooled at the temperature of solid carbon dioxide (70 C.), there were added under nitrogen 87.5 parts (4 moles/ mole alloy) of methyl chloride, containing small quantities of water as tabulated below, and weighed quantities of other additives, also as indicated below. In this system the bomb volume is such that the loading density of MeCl to bomb space is 0.35 gram/cc. The bomb was closed, immersed in a heating bath to bring the contents to reaction temperatures and the ampoule of alloy broken by striking the bomb against a solid object. The bomb was shaken vigorously at reaction temperature tor a given reaction period, then the reaction was terminated as in Example 1, the bomb opened and the reaction mixture analyzed for alloy consumption and yield of tetramethyl lead.

Results obtained with a series of such bomb runs are shown in Tables II, III and IV.

In contrast to the Tables II and III results, when normal ethylation grade ethyl chloride (containing about TABLE II.AMMONIA CATALYZED MeCl-NaPb REACTION EFFECT OF AMMONIA CONCENTRATION (60 p.p.m. H O in the MeCl; molar H O/NaPb=0.00067; reaction temp. =25 C. time=0.5 hour] It will be noted that Runs 6 and 10 of Table II are not of this invention. They show that the NH component is necessary but that excessive proportions result in a highly ineflicient reaction system as shown by the low Y/C ratio in Run 6. Furthermore, in Run 6, about 150 ppm. H O) was used in place of methyl chloride, with ammonia concentration between 0.5 and 2 wt. percent of the alloy and temperatures in the C. to C. range, tetraethyl lead was obtained in yields of less than 1%.

TABLE IV.AMMONIA CATALYZED MeCl-NaPb REACTION EFFECT OF ORGANIC HYDROXYLIC ADDITIVE [Molar NH;INaPb=0.068; H O conc.=5060 p.p.m. in MeCl reaction temp.=25 C., time=0.5 hour] Concentration Run Hydroxylic Component Y, percent C, percent Y/C Wt. percent Mole/Mole N aPb 41 49 84 2. 3 0. 16 5 0. 6 0. 043 67 82 0. 3 0. 022 85 91 93 0. 008 0. 0006 78 82 95 0. 3 0. 0093 75 88 85 0. 3 0. 012 79 0. 3 0. 012 76 85 0. 6 0. 007 79 88 0.3 0. 0073 77 91 0. 3 0.009 60 0. 3 0.022 1 nil 1 Less than 1%.

Lorol No. 5 is technical lauryl alcohol having the approximate composition by weight of 2.6% decyl alcohol, 61% lauryl alcohol, 23% myristyl alcohol, 11.2% cetyl alcohol, and 2.2% stearyl alcohol.

In summary, the tabulated data show that ammonia alone, with substantially no water, is highly effective to promote the methylation reaction under rather mild conditions (25 C. to 50 C.).

The foregoing Tables also show that water or mono- TABLE III.AMMONIA CATALYZED MeCl-NaPb REACTION EFFECT OF TEMP. AND WATER CONCENTRATION [Molar NH /NaPb=0.068; reaction time =0.5 hour] H 0 Concentration Temp., Run C. Y, percent 0, percent Y/C ppm. on Mole/Mole MeCl N aPb 25 220 0. 0027 68 77 88 25 1 2, 750 0. 024 52 61 85 25 1 4, 050 0. 037 34 42 81 25 1 5, 000 0. 047 13 25 1 67, 000 0. 63 nil 7 00 40 35 0. 0004 88 96 92 50 220 0. 0027 95 97 98 1 75 parts (3.42 moles/mole NaPb) methyl chloride.

Run 15, involving a rather large proportion of H 0 hydroxylic organic compound, whi'le essentially inopera- (corresponding to 6.7% wt. based on MeCl and 63 mole percent based on alloy), is outside the scope of this invention. Also, in Runs 13 and 14, the water is in excess of 0.3% by weight based on the methyl chloride. Runs 13-15 show, in comparison with Run 8 of Table II and Runs 11- 12 above, that the proportion of water in the catalyst system is important for openability and for achieving optimum results.

tive alone for promoting methylation, exerts the beneficial effect, in controlled amounts, of increasing alloy reaction mate (increased conversion C in a given time as shown) and of enhancing the yield Y and usually also the specificity of the re'acti011(Y/C).

Example 3 Run 8 of Table II, Example 2 was repeated with a charge consisting of 87.5 parts MeCl containing 50 ppm.

9 H 0, 1.4parts MeI, 0.5 parts NH and 100 parts NaPb. This corresponds to 4 moles MeCl, 0.068 mole NH and 0.00056 mole H O per mole of alloy, and 0.6 mole percent of Mel based on the MeCl. The yield of tetramethyl lead was 63% with Y/C=0.91. Comparison with Run 8 (44% yield of tetramethyl lead with Y/C: 0.90) shows that the small proportion of methyl iodide under these conditions has the beneficial effect of accelerating the methylation reaction.

Example 4 A 5 gallon alkylation autoclave (equipped with agitator, temperature and pressure sensing and control means, and inlet and outlet means for the addition and removal of reactants) was charged with 35 lbs. of crushed monosodium lead alloy, 1.4 lbs. of toluene and 0.4 lb. of flaked graphite. Agitation was started and the internal temperature adjusted to 25 C.30 C. To start, one lb. of methyl chloride and 0.08 8 lb. of ammonia were pressurized into the system to provide a pressure about 60 p.s.i.g. 'I hen, continuous feeding was begun simultaneously of additional methyl chloride at the rate of about 0.1 l-b./minute and of additional ammonia at the rate of about 0.0022 lb./mi-nute. Feeding of both the methyl chloride and ammonia was terminated after about 2 hours, at the end of which time a total of 10 lbs. of methyl chloride (1.3 moles/mole alloy) and 0.44 lb. of ammonia had been introduced, and during which time also the reaction temperature had been allowed to rise to a maximum of 50 C. and the pressure reached a maximum of 120 :p.s.i.g. The reaction mixture was held for 0.5 hour longer under agitation at 40 C.-50 C. and about 110-120 p.s.i.g, vented and cooled to about 25 C., discharged to a steam still and steam-distilled to obtain 7.9 lbs. of tetramethvl lead corresponding to a yield of 7 8% based on the alloy.

The methyl chloride used in this nun contained 40 ppm. water (0.004 wt. percent) whereby the molar ratio of total water introduced to alloy is 0.00014. Such conditions may be regarded as substantially water-free inasmuch as this same methyl chloride is suitable for use in the otherwise essentially anhydrous aluminum-catalyzed processes of Iarvie et a-L, in US. Patent 3,048,610 and Tullio in US. Patents 3,072,694-5. The molar ratio of ammonia to alloy in the above run is 0.17, whereby it is apparent that ammonia is highly effective in small amounts as a low-temperature, low-pressure, high-production rate catalyst for the MeCl-NaPb system.

Example 5 The procedure of Example 4, involving slow feed of both methyl chloride and ammonia, was repeated in the same equipment with the same reagents and under substantially the same conditions except that (a) there was employed a smaller total charge consisting of 18 lbs. NaPb alloy, 6.3 lbs. MeCl containing 40 ppm. H 0, and 0.26 lb.

NH corresponding to about 1.6 moles MeCl, about In the reactor of Example 4, were charged 35 lbs. of crushed NaPb, 1.4 lbs. toluene, 0.4 lb. graphite and 12 lbs. MeCl (1.56- rnoles/mole NaPb) at a pressure of about 100 p.s.i.g. The resulting mixture was warmed to 35 C. under agitation and treated with 0.11 lb. of a catalyst mixture consisting of 6.4 wt. percent methanol and 93.6 wt. percent ammonia. Following this initial increment, an additional 0.28 lb. of the catalyst mixture was fed during 1.5 hours at such a rate (about 0.0020.004 lb./minute) that the reaction mass temperature did not exceed about 40 C. and the pressure about 115 p.s.i.g. The reaction 10 mass was held at 3540 C. for 0.25 hours before being worked up as described in Example 3 to yield 9.5 lbs. of tetramethyl lead, 93.7% of theoretical.

In this run, the molar ratios of the total amount of NH H 0 (40 ppm. in the MeCl), and CH OH to alloy were 0.14, 0.00017 and 0.0058, respectively.

On repeating this procedure substantially as described above except that the methylation is effected at 60 C. and 175 p.-s.i.g. for a total reaction time of 1.33 hours, tetramethyl lead is produced in 91% yield.

Substantially the same yield (about 90%) was obtained at 60 C.65 C. (175-180 p .s.i.g.) with a smaller proportion of MeOI-I, 0.018% by weight of the alloy, 0.0013 mole/mole NaPb.

When methanol is. omitted and the conditions of the above example are otherwise substantially the same, i.e. at 60 C., the tetramethyl lead yields are -83%, where by it is apparent that methanol used according to this invention exerts a marked beneficial effect on the ammoniacatalyzed process.

11'; will be understood that the foregoing examples are given for illustrative purposes solely and that this invention is not limited to the specific embodiments described therein. On the other hand, it will be apparent to those skilled in the art that, subject to the limitations set forth in the general description, many variations can be made in the materials, proportions, conditions and techniques employed without departing from the spirit or scope of this invention.

From the foregoing description, it will be apparent that this invention provides a new and improved process for making tetramethyl lead employing a novel catalyst system. The use of such catalyst system makes it possible to efliciently manufacture tetramethyl lead in high yields and high purity under milder conditions than were possible heretofore and with a much greater degree of safety. Also, the process requires only short react-ion times, resulting in greater capacity of the equipment. Particularly, the process of this invention results in important economic advantages. Accordingly, invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process for making tetrame'thyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing at least about 1 mole of methyl chloride per mole of alloy,

(B) at a temperature of from about -20 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from 0.01 to about 1.5 moles of ammonia per mole of alloy and (b) up to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride,

(D) the total amount of water present not exceeding that specified in (b) above.

2. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 4 moles of methyl chloride per mole of alloy,

(B) at a temperature of from about 25 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from about 0.05 to about 0.6 mole of ammonia per mole of alloy and (b) from about 0.00014 to about 0.025 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride,

(D) the total amount of water present not exceeding that specified in '(b) above.

3. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 4 moles of methyl chloride per mole of alloy,

(B) at a temperature of from about 35 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from 0.05 .to about 0.3 mole of ammonia per mole of alloy and (b) from about 0.00014 to about 0.025 mole of Water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride,

(D) the total amount of water present not exceeding that specified in (b) above.

4. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing at least about 1 mole of methyl chloride per mole of alloy,

'(B) at a temperature of from about C. to about (C) in the presence of a catalyst system which consists essentially of (a) from 0.01 to about 1.5 moles of ammonia per mole of alloy,

(b) up to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride, and

(c) up to about 0.04 mole per mole of alloy of a monohydroxylic organic compound of the formula ROH wherein R represents a member of the group consisting of hydrocarbon and oxahydrocarbon radicals of 1-18 carbon atoms,

(D) the total amount of water present not exceeding that specified in (b) above.

5. The process for making tetramethyl lead which comprises reaoting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 4 moles of methyl chloride per mole of alloy,

(B) at a temperature of from about C. to about (C) in the presence of a catalyst system which consists essentially of (a) from about 0.05 to about 0.6 mole of ammonia per mole of alloy,

(b) from about 0.00014 to about 0.025 mole of water per mole of alloy, but not more than 0.3 by Weight based on the methyl chloride, and

(c) from about 0.0003 to about 0.025 mole per mole of alloy of a monohydroxylic organic compound of the formula ROH wherein R represents a member of the group consisting of hydrocarbon and oxahy-drocarbon radicals of 1-18 carbon atoms,

(D) the total amount of water present not exceeding that specified in (b) above.

6. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing at least about 1 mole of methyl chloride per mole of alloy,

(B) at a temperature of finom about 20 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from 0.01 to about 1.5 moles of ammonia per mole of alloy,

(b) up to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride, and

(0) up to about 0.04 mole of methanol per mole of alloy,

(D) the total amount of water present not exceeding that specified in (b) above.

7. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 4 moles of methyl chloride per mole of alloy,

(B) at a temperature of from about 25 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from about 0.05 to about 0.6 mole of ammonia per mole of alloy,

(b) from about 0.00014 to about 0.025 mole of water per mole of alloy, but not more than 0.3 by weight based on the methyl chloride, and

(-c) from about 0.0003 to about 0.025 mole of methanol per mole of alloy,

(D) the total amount of Water present not exceeding that specified in (b) above.

8. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 3 moles of methyl chloride per mole of alloy,

(B) at a temperature of from about 35 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from about 0.05 to about 0.3 mole of ammonia per mole of alloy,

(b) from about 0.00014 to about 0.003 mole of water per mole of alloy, but not more than 0.3 by Weight based on the methyl chloride, and

(c) from about 0.0003 to about 0.025 mole of methanol per mole of alloy,

(D') the total amount of water present not exceeding that specified in (b) above.

9. The process for making .tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing at least about 1 mole of methyl chloride per mole of alloy,

(B) at a temperature of from about 20 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from 0.01 to about 1.5 moles of ammonia per mole of alloy,

(b) from 0 .to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride, and

(c) from 0 to about 0.4 mole per mole of alloy of a monohydroxylic organic compound of the formula ROH wherein R represents a member of the group consisting of hydrocarbon and oxahydrocarbon radicals of 1-18 carbon atoms,

(D) the total amount of water present not exceeding that specified in (b) above.

10. The process for making tetramethyl lead which comprises reacting monosodium lead alloy with (A) a methylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 4 moles of methyl chloride per mole of alloy,

1.3 (B) at a temperature of from about 25 C. to about 85 C. (C) in the presence of a catalyst system which consists essentially of (a) from about 0.05 to about 0.6 mole of ammonia per mole of alloy,

(b) from 0 to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on the methyl chloride, and

(c) from 0 to about 0.4 mole per mole of alloy of a monohydroxylic organic compound of the formula ROH wherein R Iepresents a member of the group consisting of hydrocarbon and oxahydrocarbon radicals of 1-l8 carbon atoms,

(D) .the total amount of water present not exceeding that specified in (b) above.

11. The process for making tetnarnethyl lead which comprises reacting monosodium lead alloy with (A) .a melthylating agent which consists essentially of methyl chloride in the liquid phase, employing from about 1.3 to about 4 moles of methyl chloride per mole of alloy,

(B) at a temperature of from about 35 C. to about (C) in the presence of a catalyst system which consists essentially of (a) from 0.0 5 to about 0.3 mole of ammonia per mole of alloy,

(b) from 0 to about 0.04 mole of water per mole of alloy, but not more than 0.3% by weight based on .the methyl chloride, and

(-c) from 0 to about 0.04 mole per mole of alloy of a monohydroxylic organic compound of the formula ROH wherein R vrepresents a member of the group consisting of hydrocarbon and oxahydr-ooarbon radicals of 118 carbon atoms,

(D) the total amount of water present not exceeding that specified in (b) above.

References Cited by the Examiner UNITED STATES PATENTS 1,559,405 10/ 1925 Calcott 260'-437 1,622,228 3/1927 Midgley 260437 1,661,809 3/1928 Monroe 260-437 TOBIAS E. LEVOW, Primary Examiner.

E. C. BARTLETT, H. M. SNEED, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3, 281, 442 October 25 1966 Rudolph Lo Pedrotti et al9 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 48, for "The" read They line 63, for "require elevated" read require rather elevated column 2, line 30, for "to 0004" read to about 0004 column 3, line 7, for "radidly" read rapidly line 16, for "ammonia-catalpzed" read ammonia-catalyzed line 75, for "(cetyl alcohol and" read (cetyl alcohol) and column 8, line 18, for "Concentration" read Concentrations column 13, line 10, for "004" read 0004 O Signed and sealed this 5th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

9. THE PROCESS FOR MAKING TETRAMETHYL LEAD WHICH COMPRISES REACTING MONOSODIUM LEAD ALLOY WITH (A) A METHYLATING AGENT WHICH CONSISTING ESSENTIALLY OF METHYL CHLORIDE IN THE LIQUID PHASE, EMPLOYING THE LEAST ABOUT 1 MOLE OF METHYL CHLORIDE PER MOLE OF ALLOY, (B) AT A TEMPERATURE OF FROM ABOUT -20*C. TO ABOUT 120*C. (C) IN THE PRESENCE OF A CATALYST SYSTEM WHICH CONSISTS ESSENTIALLY OF (A) FROM 0.01 TO ABOUT 1.5 MOLES OF AMMONIA PER MOLE OF ALLOY, (B) FROM 0 TO ABOUT 0.04 MOLE OF WATER PER MOLE OF ALLOY, BUT NOT MORE THAN 0.3% BY WEIGHT BASED ON THE METHYL CHLORIDE, AND (C) FROM 0 TO ABOUT 0.4 MOLE PER MOLE OF ALLOY OC A MONOHYDROXYLIC ORGANIC COMPOUND OF THE FORMULA ROH WHEREIN R REPRESENTS A MEMBER OF THE GROUP CONSISTING OF HYDROCARBON AND OXAHYDROCARBON RADICALS OF 1-18 CARBON ATOMS, (D) THE TOTAL AMOUNT OF WATER PRESENT NOT EXCEEDING THAT SPECIFIED IN (B) ABOVE. 